Conventionally, sheet handling apparatuses continuously take out and convey a plurality of stacked sheets one by one. Such a sheet handling apparatus furthermore inspects the conveyed sheets and stacks the inspected sheets in a predetermined stacking portion in accordance with the inspection result.
In this sheet handling apparatus, for example a rotating drum of a take-out portion that rotates while contacting stacked sheets, and conveyor belts of a conveyor portion that run while sandwiching the sheets that have been taken out are connected to a single driving motor via a timing belt. The take-out portion and the conveyor portion are driven while being mechanically synchronized.
Thus, even if for some reason there is a variation in the rotation speed of the driving motor, operational deviations between the take-out portion and the conveyor portion can be prevented.
Moreover, as this kind of sheet handling apparatus, a type is known in which the sheets are adsorbed to the surface of a take-out rotor and then taken out onto the conveying path. In apparatuses of this kind, negative pressure is generated at the surface of the take-out rotor and the sheets are adsorbed thereto, so that in order to reliably adsorb the sheets to the rotor surface, a method is conceivable in which the rotation speed is slowed down during the time of adsorption.
For example, if a take-out rotor of the above-described negative pressure/adsorption type is used in an apparatus in which the take-out portion and the conveyor portion are mechanically synchronized, then, if the rotation speed of the take-out rotor is slowed in order to favorably adsorb the sheets, the conveying speed of the sheets at the conveyor portion has to be made slow as well. Conversely, if the rotation speed of the take-out rotor is increased in order to increase the conveying speed at the conveyor portion, then the adsorption of the sheets becomes insufficient and take-out problems may occur.
On the other hand, the physical parameters (friction coefficients and the like) of the conveying belts may fluctuate due to various external factors such as temperature and dampness, and there may also be variations among individual belts. Furthermore, when the load acting on the conveying belts changes, also the rotation speed of the motors driving the conveying belts changes. Therefore, the conveying speed of the sheets in the conveyor portion tends to fluctuate.
When the conveying speed of the sheets fluctuates, the conveying pitch fluctuates, erroneous determinations may be made by the inspection portion, separation mistakes may occur at the separating portion, and there is the possibility that stacking mistakes occur at the stacker.